Font Size Testing

All of the following are identical according to the CSS spec if
you assume a 96dpi screen set to a starting point of 12pt or 16px
(96dpi implies 4:3 pixels to points).

"Absolute" Sizes

This is — 24pt.

This is — 2 pica.

This is — 8.47mm.

This is — 0.333in.

Relative Sizes

This is — 32px.

This is — 200%.

This is — 2em.

Notes

In Chrome on Linux, with a 100dpi screen, these look identical,
and the width of the em dash is about 8.5mm measured with a
ruler. In Firefox on Linux, they are also identical (or nearly),
and visually bigger, but the length of the em dash is slightly
smaller, around 7.5mm. Neither Firefox nor Chrome specify the
units in teh font size selection dialog, but they are both set to
a unitless "16".